Induction heater for cooking

ABSTRACT

An induction-heating cooking device includes a light-transmissive cooking board on which a cooking container to be heated is to be placed; a heating coil for heating the cooking container; light emission means for emitting a light beam; and light-transmissive light conducting means for allowing the light beam emitted by the light emission means to be propagated therethrough. The light beam lights up an outer peripheral portion of the light conducting means.

TECHNICAL FIELD

The present invention relates to an induction-heating cooking deviceused in general households.

BACKGROUND ART

Recently, an induction-heating cooking device is a target of attentionas a safe heating cooking device. Conventionally, this type ofinduction-heating cooking device generally represents its heating statewith a display section, which is provided in the vicinity of an outputsetting section and lit up with, for example, a light bulb or asemiconductor device. Some built-in type induction-heating cookingdevices, in which the output setting section and the cooking section arevisually separated from each other, have another similar display sectionon a front part of the cooking section. Hereinafter, a structure of aconventional induction-heating cooking device 3600 will be describedwith reference to FIG. 36.

As shown in FIG. 36, the induction-heating cooking device 3600 includesa case 6001 forming a main body, a cooking board 6003 on which a cookingcontainer 6002 to be heated is to be placed, a heating coil 6004 locatedbelow the cooking board 6003, a temperature sensor 6005 for sensing thetemperature of the cooking container 6002, an output control section6006 for controlling an output of the heating coil 6004, a ventilator6007 for cooling the output control section 6006, a power switch 6008for turning on/off the power, a power display section 6009 fordisplaying the on/off state of the power switch 6008, an output settingsection 6010 for setting the output, an output display section 6011 fordisplaying the setting state of the output, a second output displaysection 6012 located in a front area of the cooking board 6003, and aheating state display section 6013 for displaying the heating state.

The induction-heating cooking device having the above-describedstructure operates as follows. When the power switch 6008 is turned on,the power display section 6009 is lit up so as to display the on/offstate of the power switch. When the cooking container 6002 accommodatingfood to be cooked is placed on the cooking board 6003 and the outputsetting section 6010 is turned on, the output display section 6011 islit up so as to display the setting state of the output and also startheating. Simultaneously, the second output display section 6012 is litup so as to display the setting state of the output. In accordance withthe temperature sensed by the temperature sensor 6005, the heating statedisplay section 6013 is lit up so as to display the heating state.

Conventionally, this type of induction-heating cooking device does notgenerate a flame and have a high thermal efficiency, unlike a gascooking stove. Therefore, the demand for this type of induction-heatingcooking device is increasing. FIG. 37 is an isometric view of aconventional, general induction-heating cooking device 3700. In FIG. 37,reference numeral 6101 represents a main body case, reference numeral6102 represents a cooking board on which a cooking container to beheated is to be placed, reference numerals 6103 and 6104 representheating sections using induction heating of the same rated outputs andcorresponding to heating coils (not shown) provided below the cookingboard 6102. Reference numeral 6105 represents a radiation heater usedfor heating an aluminum pan or a copper pan which cannot be heated byinduction heating.

For performing induction-heating cooking using the induction-heatingcooking device 3700 having the above-described structure, a cookingcontainer which can be induction-heated is placed on the heating section6103 or 6104 of the cooking board and the power is turned on.

An induction-heating cooking device performs cooking as follows. A highfrequency electric current is caused to flow to a heating coil so as togenerate a high frequency magnetic field. A Joule heat by an eddycurrent is generated in a pan (load) which is magnetically coupled tothe heating coil, so as to heat the pan itself. Therefore, there is aproblem in that the user cannot easily recognize the heating statevisually, unlike with a gas cooking device generating a flame or anelectric heater in which the heating section is heated red.

In order to solve this problem, for example, an induction-heatingcooking device described in Japanese Patent No. 2903561 is proposed.With reference to FIG. 38, a conventional induction-heating cookingdevice 3800 will be described. As shown in FIG. 38, theinduction-heating cooking device 3800 includes a heating coil 6202 forheating a pan located below a cooking board 6201 by induction heating,and light bulbs 6203 provided in the vicinity of the heating coil 6202.Japanese Patent No. 2903561 discloses that (i) simultaneously with aheating operation, the light bulbs 6203 provided in the vicinity of theheating coil 6202 are lit up so as to display a heating area; and (ii)when a substance which generates light when receiving light is caused toadhere to a bottom surface of an iron plate provided on a top surface ofthe main body, a pan is put in place and a heating operation is started,the light bulb 6203 provided at the center of the heating coil emitslight; and upon receiving the light, the substance secondarily emitslight, resulting in a circle 6204 as shown in FIG. 39 being displayed onthe cooking board.

Japanese Laid-Open Publication No. 7-312279 describes the following. Aplurality of light emitting diodes for displaying the heating state areprovided along an outer periphery of the heating coil, and a lightemitting diode for displaying the heating power is provided in thevicinity of and outside the plurality of light emitting diodes. When theheating coil is electrically conducted so as to be heated, the lightemitting diodes for displaying the heating state are lit up. Thus, theheating state is notified. The light emitting diode provided in thevicinity thereof for displaying the heating is lit up. Thus, the heatingpower is clearly indicated.

With reference to FIG. 40, an induction-heating cooking device 4000includes a heating coil 6302 for heating a pan provided below a cookingboard 6301 by induction heating, and light bulbs 6303 provided in thevicinity of the heating coil 6302. Simultaneously with a heatingoperation, the light bulbs 6303 provided in the vicinity of the heatingcoil 6302 are lit up so as to display heating area.

With reference to FIG. 41, it is proposed to provide, below the heatingcoil, a circularly annular conductor 6304 formed by assembling aplurality of blocks, each including a conductor piece 6304 a and a lightsource 6305. According to this structure, the plurality of light sources6305 are provided at the center of the circularly annular conductor.When the heating coil is electrically conducted to be heated, the lightsources 6305 are lit up along an outer periphery of the circularlyannular conductors 6304. In this manner, the heating state is indicated.

According to the conventional method, as shown in FIG. 36, of displayingthe heating state of the induction-heating cooking device 3600, thesection for actually performing cooking and the section for displayingare visually separated from each other. Therefore, it is difficult forthe user to visually recognize the heating state.

The induction-heating cooking device, which outputs invisible alternatemagnetic fluxes, has a specific problem of being difficult to handlesince it is difficult for the user to visually recognize the heatingstate, unlike with a gas cooking device generating a visible flame.

With induction-heating cooking devices, the user cannot visuallyrecognize the heating state. Therefore, for safety, heating is generallystarted after the power is turned on, a cooking container is placed onthe cooking board, and the heating power is set. As described withreference to the conventional examples, various methods have beenproposed for allowing the user to visually recognize whether heating isperformed or not. However, the on/off state of the power has not beenmuch considered. Even when the cooking container is placed on thecooking board, it is not shown whether the power is on or off.Therefore, the user needs to check with the power display section eachtime. However, the power display section is small and far from theheating section for heating the cooking container. Thus, it istroublesome to check from time to time when the user is busy orcontinuously cooking.

The plurality of heating sections in the conventional induction-heatingcooking device 3700 shown in FIG. 37 all use the heating coils of thesame rating. For example, in FIG. 37, there are two heating sections(the heating sections 6103 and 6104). The heating coils corresponding tothem both have a rated output of 2 kW.

As a wider variety of foods have become cooked in a wider variety ofmanners recently, there is a demand for heating sections havingdifferent outputs, especially large outputs. The present inventionprovides an induction-heating cooking device including heating coilshaving different ratings, i.e., heating sections having different inputsand outputs.

Even if the heating sections have different outputs, the differencecannot be represented with an induction-heating cooking device. Inconventional induction-heating cooking devices, it does not matter whichone of the heating sections is used for which cooking container. This istrue when cooking containers are placed on both the heating sections, oreven when one cooking container is placed on one of the heatingsections.

When the heating sections have different outputs, a wrong selection ofthe heating section results in the cooking time being different from theexpected time or the cooking being finished in a poor state due to anexcessive temperature rise.

The conventional induction-heating cooking device 3800 shown in FIG. 38includes light emitting means, for example, light bulbs 6203 in thevicinity of the heating coils 6202. This structure requires a pluralityof light bulbs for displaying the heating sections corresponding to theheating coils 6202. When the number of light bulbs is limited, theheating section is difficult to see since the display is provided bydots.

A display method utilizing secondary light emission, which allowsgeometrical figures, such as circles, to be drawn relatively easily, hasnot been put into practice due to the following problems: (i) thedisplay is faint and difficult to see due to the poor efficiency of thesecondary light emission; (ii) a clear geometrical figure is difficultto draw due to the directivity or attaching dispersion of the light bulb6203 used for light emission which are provided at the center of theheating coil; and (iii) the stability is poor since the secondary lightemitting substance is provided below the cooking board 6201 having ahigh temperature.

The structures shown in FIGS. 40 and 41 both use a plurality of lightsources. The structure is a one-system structure in which all theplurality of light sources are connected in series. Therefore, if even apart thereof malfunctions, the entire system remains unlit, whichprevents the user from visually recognizing the heating section.

The pattern is limited to two: (i) lighting-up and (ii) blinking. Thus,it is impossible to provide various manners of display.

An objective of the present invention is to provide a highly safeinduction-heating cooking device having an improved ease of handling byallowing a heating state to be displayed in a similar manner to that ofa gas cooking device.

Another aspect of the present invention is to provide aninduction-heating cooking device which allows the on/off state of thepower to be easily checked and also allows whether the heating isperformed or not to be easily checked.

Still another aspect of the present invention is to provide aninduction-heating cooking device which allows a difference in outputs tobe recognized with a simple structure.

Still another aspect of the present invention is to provide aninduction-heating cooking device which can clearly display the heatingarea and its vicinity of the heating section corresponding to theheating coil with a small number of light sources.

Still another aspect of the present invention is to provide aninduction-heating cooking device which allows the heating section to bevisually recognized by preventing the entirety of a heating section fromfailing lighting up even if a part of the heating section malfunctions,and which allows various patterns to be provided.

DISCLOSURE OF THE INVENTION

An induction-heating cooking device according to the present inventionincludes a light-transmissive cooking board on which a cooking containerto be heated is to be placed; a heating coil for heating the cookingcontainer; light emission means for emitting a light beam; andlight-transmissive light conducting means for allowing the light beamemitted by the light emission means to be propagated therethrough. Thelight beam lights up an outer peripheral portion of the light conductingmeans. Thus, the above-described objectives are achieved.

The light emission means and the light conducting means may be providedoppositely to each other with respect to the heating coil.

The light conducting means may be disc-shaped. The light conductingmeans may have an opening at a center thereof. The light emission meansmay be provided in the opening.

The light conducting means may have a thickness which decreases from aninner portion to an outer portion. The light conducting means may have atop surface and a bottom surface. The induction-heating cooking devicemay further include reflection means provided on at least the topsurface and the bottom surface for reflecting the light beam.

The light conducting means may have an illumination surface formed at anouter peripheral end of the light conducting means for reflecting thelight beam toward the cooking board.

The induction-heating cooking device may further include reflectionmeans provided parallel to the illumination surface for reflecting thelight beam toward the cooking board.

The light conducting means may further have a wall formed on the side ofthe cooking board with respect to the illumination surface for guidingthe light beam toward the cooking board. The wall may have a top surfacefacing the cooking board. The top surface may have display meansprovided thereon for randomly reflecting or diffusing the light beam.

Another induction-heating cooking device according to the presentinvention includes a light-transmissive cooking board on which a cookingcontainer to be heated is to be placed; a heating coil for heating thecooking container; light emission means for emitting a light beam; andlight-transmissive light conducting means for allowing the light beamemitted by the light emission means to be propagated therethrough. Thelight conducting means is formed on a border section on which the lightbeam emitted by the light emission means is incident, and has a concavesurface facing the light emission means. Thus, the above-describedobjectives are achieved.

Still another induction-heating cooking device according to the presentinvention includes a light-transmissive cooking board on which a cookingcontainer to be heated is to be placed; a heating coil for heating thecooking container; a coil base for fixing the heating coil; lightemission means for emitting a light beam; and light-transmissive lightconducting means for allowing the light beam emitted by the lightemission means to be propagated therethrough. The light conducting meansis fixed on the coil base. Thus, the above-described objectives areachieved.

Still another induction-heating cooking device according to the presentinvention includes a light-transmissive cooking board on which a cookingcontainer to be heated is to be placed; a heating coil for heating thecooking container; light emission means for emitting a light beam; andlight-transmissive light conducting means for allowing the light beamemitted by the light emission means to be propagated therethrough. Theheating coil is fixed on the light conducting means. Thus, theabove-described objectives are achieved.

Still another induction-heating cooking device according to the presentinvention includes a light-transmissive cooking board on which a cookingcontainer to be heated is to be placed; a heating coil for heating thecooking container; light emission means for emitting a light beam; andlight-transmissive light conducting means for allowing the light beamemitted by the light emission means to be propagated therethrough. Thelight emission means is fixed on the light conducting means. Thus, theabove-described objectives are achieved.

The induction-heating cooking device may further include a coil base forfixing the heating coil.

Still another induction-heating cooking device according to the presentinvention includes a light-transmissive cooking board on which a cookingcontainer to be heated is to be placed; a heating coil for heating thecooking container; output control means for controlling an output of theheating coil; ventilation means for generating a cooling air for coolingthe output control means; light emission means for emitting a lightbeam; and light-transmissive light conducting means for allowing thelight beam emitted by the light emission means to be propagatedtherethrough. The cooling air cools the light emission means and thelight conducting means. Thus, the above-described objectives areachieved.

The cooling air may cool the light emission means and the lightconducting means after cooling the output control means.

Still another induction-heating cooking device according to the presentinvention includes a light-transmissive cooking board on which a cookingcontainer to be heated is to be placed; a heating coil for heating thecooking container; a plurality of light emission means for emitting alight beam; and light-transmissive light conducting means for allowingthe light beam emitted by the plurality of light emission means to bepropagated therethrough. The light conducting means includes lightconducting blocks corresponding to the plurality of light emissionmeans. Thus, the above-described objectives are achieved.

Still another induction-heating cooking device according to the presentinvention includes a light-transmissive cooking board on which a cookingcontainer to be heated is to be placed; at least one heating sectionprovided on the cooking board for heating the cooking container byinduction heating; a heating coil provided oppositely to the cookingcontainer with respect to the cooking board, the heating coil beingprovided in correspondence with the heating section; display means fordisplaying a use state of the heating section; and control means forcontrolling the display means. The control means displays the use statein the vicinity of the heating section by the display means when poweris turned on. Thus, the above-described objectives are achieved.

The control means may change a form of a display in the vicinity of theheating section when the cooking container is placed and heated by theheating coil.

When an output is not set for a prescribed time period after the poweris turned on, the control means may turn the power off.

The induction-heating cooking device may include a plurality of heatingsections. When an output is not set for at least one of the heatingsections for a prescribed time period after the power is turned on, thecontrol means may delete a display corresponding to the heating sectionfor which the output is not set.

The induction-heating cooking device may include a plurality of heatingsections. When the power is turned on, a use state of at least one ofthe heating sections may be displayed in the vicinity of the at leastone of the heating sections.

The control means may change the form of the display in the vicinity ofthe heating section from blinking to lighting-up.

The control means may change a color of the display in the vicinity ofthe heating section.

Still another induction-heating cooking device according to the presentinvention includes a plurality of heating sections provided on a cookingboard for heating a cooking container placed thereon by inductionheating; a plurality of heating coils having different outputs providedoppositely to the cooking container with respect to the cooking board,the plurality of heating coils being provided in correspondence with theplurality of heating sections; and light emission means for emitting alight beam. The light emission means displays graphic patterns on thecooking board for allowing a difference in the outputs of the heatingcoils to be visually recognized. Thus, the above-described objectivesare achieved.

The outputs may include a rated output.

The outputs may include a set output.

The difference in the outputs may be represented by a difference in sizeof the graphic patterns.

The difference in the outputs may be represented by a difference inwidth of the graphic patterns.

The difference in the outputs may be represented by a difference innumber of the graphic patterns.

When the difference in the outputs is represented by a difference innumber of similar graphic patterns, one of the heating section may berepresented by a single graphic pattern and the other heating sectionmay be represented by at least two similar graphic patterns.

The difference in the outputs may be represented by at least one of adifference in color of the graphic patterns or a difference in colordarkness of the graphic patterns.

The difference in the outputs may be represented by at least one of adot, a straight line, or a polygon.

There may be two heating coils. The light emission means may display agraphic pattern for at least one of the heating coils on the cookingboard so as to allow a difference in the outputs of the heating coils tobe visually recognized.

The light emission means may emit light during cooking, and blinks thelight after the cooking is finished until a temperature of the cookingboard decreases to a safe level.

Still another induction-heating cooking device according to the presentinvention includes a light-transmissive cooking board provided on a topsurface of a main body case; a heating section provided on the cookingboard for heating a cooking container placed thereon by inductionheating; a heating coil provided oppositely to the cooking containerwith respect to the cooking board, the heating coil being provided incorrespondence with the heating section; a light conducting bodyprovided at a position corresponding to an outer peripheral portion ofthe heating coil; and a light source for emitting a light beam towardthe light conducting body. The light conducting body receives the lightbeam emitted by the light source and outputs the light beam from aposition corresponding to at least a part of the outer peripheralportion of the heating coil toward the cooking board. Thus, theabove-described objectives are achieved.

The light conducting body may have a top surface formed so as to facethe cooking board and a bottom surface formed oppositely to the cookingboard with respect to the top surface. The bottom surface may have aninclination formed such that a distance between the top surface and thebottom surface decreases in a direction away from the light source.

The light conducting body may have a random reflective layer formed onthe bottom surface for randomly reflecting the light beam.

The light conducting body may have a mirror surface reflective layerformed on the bottom surface for subjecting the light beam with mirrorsurface reflection.

The light conducting body may have a sawtooth-shaped prism formed on thebottom surface.

The induction-heating cooking device may further include a layer formedon a surface other than the top surface for guiding the light beam, thelight having a smaller refractive index than that of the lightconductive body.

The bottom surface may be formed so as to partially change thereflectance of the light beam.

The light conducting body may be donut-shaped.

Still another induction-heating cooking device according to the presentinvention includes a light-transmissive cooking board provided on a topsurface of a main body case; a heating section provided on the cookingboard for heating a cooking container placed thereon by inductionheating; a heating coil provided oppositely to the cooking containerwith respect to the cooking board, the heating coil being provided incorrespondence with the heating section; a plurality of first lightsources and a plurality of second light sources for emitting lightbeams; and a light conducting body for guiding the light beams emittedby the plurality of first light sources and the plurality of secondlight sources and outputting the light beam at a position correspondingto an outer peripheral portion of the heating coil. The plurality offirst light sources and the plurality of second light sources areconnected parallel to each other. Thus, the above-described objectivesare achieved.

The plurality of first light sources and the plurality of second lightsources maybe connected in the form of blocks.

The plurality of first light sources and the plurality of second lightsources may be connected alternately.

The light conducting body may be annular. The plurality of first lightsources and the plurality of second light sources may be arranged in anannular form at a center of the light conducting body.

The light conducting body includes a plurality of light conductive bodypieces. A plurality of blocks, each including the light conducting bodypiece and at least two light sources, may be combined.

The light conducting body may include a wall extending vertically towardthe cooking board from an outer peripheral end thereof. The light beamsmay be directed from the top surface of the wall toward the cookingboard.

The plurality of first light sources and the plurality of second lightsources may alternately blink.

The induction-heating cooking device may further include a plurality ofthird light sources for emitting light beams. The plurality of firstlight sources, the plurality of second light sources, and the pluralityof third light sources may sequentially blink.

The induction-heating cooking device may further include lead sectionsfor connecting the plurality of first light sources. The lead sectionsmay be provided radially around a center of the light conducting body.

Each of the lead sections may be twisted.

According to one aspect of the invention, an outer peripheral portion ofthe light conducting means is lit up. Then, the light beam istransmitted through the light-transmissive cooking board, and theheating state can be displayed on the top surface of the cooking board.Accordingly, the display which is visually separated from the cookingsection in a conventional apparatus can be provided in the vicinity ofthe cooking section. Thus, the induction-heating cooking device can beused in a similar manner to that of a gas cooking device.

The light conducting means and the light emitting means are providedbelow the heating coil. Owing to such a structure, the light beam isprevented from leaking to an area immediately above the light emittingmeans. In the case where the light conducting means is formed of a resinor the like, discoloring, deformation or the like of the lightconducting means caused by the thermal influences of radiation,conductance or transmission from the cooking container or the like canbe prevented. Reduction in the reliability or the like due tomalfunction caused by the thermal influences of the strong magneticfield or self-heat generation can be prevented. Reduction in theluminous intensity or the like caused by a temperature rise of the lightemitting means can be prevented.

The light conducting means is disc-shaped and has an opening at thecenter thereof. The light emitting means is provided in the opening ofthe light conducting means. Owing to such a structure, a display whichis uniform in luminous intensity can be provided.

The thickness of the light conducting means is greatest in an innerportion and decreases toward an outer portion. Reflection means isprovided on a top surface or a bottom surface of the light conductingmeans. Owing to such a structure, the loss of the light beam at the timeof incidence is reduced. The reflective means reduces the loss of thelight beam during propagation. Therefore, a display having a higherluminous intensity with less loss can be provided.

The light conducting means has an illumination surface (a surface havingan angle of, for example, 45 degrees with respect to the lightpropagation direction) at an outer peripheral end of the lightconducting means. Owing to such a structure, the propagated light issubjected to total reflection so as to guide the light beam toward thecooking board, i.e., a cooking surface.

Reflection means is provided parallel to the illumination surfaceprovided at the outer peripheral end of the light conducting means.Thus, the loss of the light beam caused at the time of total reflectiondue to dispersion during production can be reduced.

A wall is provided on a top surface of the illumination surface which isprovided at an outer peripheral end of the light conducting means.Display means for randomly reflecting or diffusing a light beam whichhas been propagated to the top surface of the wall is provided. Owing tosuch a structure, the display can be provided at a position closer tothe cooking board.

A concave surface facing the light emitting means is provided at aborder section of the light conducting means. (The border portion has aproperty of collecting light beams when having a convex surface facingthe light emitting means, and dispersing the light beams when having aconcave surface facing the light emitting means). Owing to such astructure, the refraction angle can be increased. Thus, even when lightemitting means having a small directivity angle is used, a highlyluminous, wide range display can be provided.

The light conducting means is fixed to a coil base. Owing to such astructure, the position of the display provided by the light conductingmeans with respect to the position of the heating area can berestricted.

The light emitting means is fixed to the light conducting means. Owingto such a structure, the position of the display provided by the lightconducting means with respect to the position of the light emittingmeans can be restricted.

The structure in which the output control means is cooled and then thelight emitting means and the light conducting means are cooled isprovided. Owing to such a structure, reduction in the luminous intensitydue to a temperature rise of the light emitting means is prevented, anddiscoloring, deformation or the like of the resin used for the lightconducting means can be prevented.

The light conducting means is provided in blocks. Owing to such astructure, repairing can be easily and rapidly performed by replacingonly the block which malfunctions.

According to another aspect of the invention, the on/off state of thepower can be easily recognized in the vicinity of the heating-cookingcontainer, and whether heating is being performed or not can be easilyrecognized. Thus, the induction-heating cooking device can be easilyused. When the power is turned on, it is informed by the displayprovided in the vicinity of the heating section. Therefore, it is easilyvisually recognized that the power is on.

When the power is turned on, the control means displays that state inthe vicinity of the heating section by the display means. When thecooking container is placed and heated, the control means changes theform of the display. Since the form of the display is visually changedin the vicinity of the cooking container, the on/off state of the powerand the heating state can be easily confirmed.

When the output is not set for a prescribed time period after the poweris turned on, the control means turns the power off. In the case wherethe induction-heating cooking device includes a plurality of heatingsections using induction heating, and there is a heating section forwhich the output is not set for a prescribed time period after the poweris turned on, the control means deletes the display for the heatingsection. In an induction-heating-cooking device including a plurality ofheating sections using induction heating, when the power is turned on,that state is displayed in the vicinity of at least one of the heatingsections. Since the number of heating sections for which display isprovided is minimized in this manner, the power can be saved. Thedisplay can be changed from blinking to lighting-up. The display can bechanged by changing the color. Since the display can be changed by acombination of blinking/lighting-up and the change of color, visualrecognition can be easily provided.

According to still another aspect of the invention, different outputsare represented by different graphic patterns. Therefore, an appropriateheating section can be easily selected. Specifically, the difference inthe rated output is represented by the difference in size of the graphicpatterns, the difference in width of the graphic patterns, thedifference in number of the graphic patterns, or whether a singlegraphic pattern or at least two similar graphic patterns are provided.Alternatively, the difference in the rated output is represented by atleast one of the difference in color of the graphic patterns or thedifference in color darkness of the graphic patterns.

Using such differences, the rated outputs of the heating sections can bevisually distinguished easily. The graphic pattern is at least one of adot, a straight line or a polygon. Since the graphic patterns aresimple, the structure of the light emitting means required for thedisplay can be simple. In the case where there are two heating coils,the graphic pattern is provided for one of the two heating coils. Thus,the rated outputs of the heating sections can be distinguished easily.The light emitting means lights up during cooking, and blinks after thecooking is finished until the temperature is decreased to a safe level.Due to such a structure, the proceeding state of the cooking can beeasily recognized.

According to still another aspect of the invention, the display isprovided around the entirety of the outer periphery of the heatingsection. Therefore, the heating section can be clearly represented onthe cooking board. Since a clear continuous graphic pattern is displayedon the cooking board, the heating state can be easily recognized. Sincea straight light beam from the light source can reach a position farfrom the light source, the entirety of the light conducting means lightsup uniformly. Since the reflected light from an area below the lightconducting means uniformly reaches an area above the light conductingmeans, the display is uniform. Since there is little loss by lightleakage, a clear graphic pattern can be provided on the cooking board.Graphic patterns having different levels of darkness can be provided onthe cooking board. Where the heating coil is circular, the heatingsection can be clearly represented.

According to still another aspect of the invention, even when one systemof light sources malfunctions, the other system of light sources keep onlighting up. Since there are a plurality of systems, various displaypatterns can be combined. Even when one system of light sourcesmalfunctions, the other system of light sources keep on lighting up.Therefore, the heating section can be visually recognized. Thus, thesafety level is improved. Since there are a plurality of systems, thenumber of combinations of the systems is increased, which also increasesthe number of display patterns.

For example, the type, color, size or brightness of the light sourcescan be changed system by system, or the light sources can be lit up,blinked or extinguished system by system. Such changes can be setarbitrarily by the designer in accordance with the function of thedevice, the state of the device, the use state of the device, or time.

At least two systems of light sources can be connected as a block. Inthis case, even if one system malfunctions, the other system keeps onlighting up. Therefore, the heating section can be visually recognized,and the malfunction is easily recognized. At least two systems of lightsources can be alternately connected. In this case, even if one systemmalfunctions, the other system keeps on lighting up. Therefore, theheating section can be visually recognized, and a malfunction is easilyrecognized due to the reduction in the light amount.

The light conducting means can be circularly annular, and a plurality oflight sources can be provided in a circularly annular form at the centerof the light conducting means. In this case, displays are providedcontinuously on the cooking board. When there is a place where nodisplay is provided or where the brightness of the display is lower, amalfunction can be easily recognized.

Two systems of light sources can be alternately lit up. Since one of thesystems is always lit up, this structure provides the sense of safety.When different colors are used for different systems, visual recognitioncan be improved. When the systems are not alternately lit up, amalfunction can be easily recognized. At least three systems of lightsources can be provided such that each system is lit up. This structurefurther avoids a situation where visual recognition cannot be provideddue to a malfunction. In the case where the systems are lit upsequentially, a malfunction can be easily recognized.

The leads of the light sources can be twisted. This further preventsmalfunction or heat generation due to the magnetic field caused byinduction heating.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an induction-heating cooking deviceaccording to a first example of the present invention.

FIG. 2( a) shows one state of a cooking board of the induction-heatingcooking device according to the first example of the present invention.

FIG. 2( b) shows another state of the cooking board of theinduction-heating cooking device according to the first example of thepresent invention.

FIG. 2( c) shows still another state of the cooking board of theinduction-heating cooking device according to the first example of thepresent invention.

FIG. 3 is an isometric view of light conducting means of theinduction-heating cooking device according to the first example of thepresent invention.

FIG. 4 is a cross-sectional view of an induction-heating cooking deviceaccording to the first example of the present invention.

FIG. 5 is a cross-sectional view of another induction-heating cookingdevice according to the first example of the present invention.

FIG. 6 is a cross-sectional view of still another induction-heatingcooking device according to the first example of the present invention.

FIG. 7 is a cross-sectional view of still another induction-heatingcooking device according to the first example of the present invention.

FIG. 8( a) is an exploded isometric view of an induction-heating cookingdevice according to a second example of the present invention.

FIG. 8( b) is a partial expanded view of light conducting means of theinduction-heating cooking device according to the second example of thepresent invention.

FIG. 9( a) is a partial expanded view of light conducting means of aninduction-heating cooking device according to the second example of thepresent invention.

FIG. 9( b) is a partial expanded view of light conducting means inanother form of an induction-heating cooking device according to thesecond example of the present invention.

FIG. 10 is a cross-sectional view of an induction-heating cooking deviceaccording to a third example of the present invention.

FIG. 11 is a cross-sectional view of the induction-heating cookingdevice according to the third example of the present invention.

FIG. 12 is a partial expanded view of light conducting means of theinduction-heating cooking device according to the third example of thepresent invention.

FIG. 13 is a cross-sectional view of an induction-heating cooking deviceaccording to a fourth example of the present invention.

FIG. 14( a) is a partial expanded view of light conducting means and thevicinity thereof of the induction-heating cooking device according tothe fourth example of the present invention.

FIG. 14( b) is a partial expanded view of light conducting means and thevicinity thereof in another form of an induction-heating cooking deviceaccording to the fourth example of the present invention.

FIG. 15 is a cross-sectional view of an induction-heating cooking deviceaccording to a fifth example of the present invention.

FIG. 16 is a partial expanded view of the induction-heating cookingdevice according to a fifth example of the present invention.

FIG. 17 is an isometric view of an induction-heating cooking deviceaccording to fourth through sixth examples of the present invention.

FIG. 18 is a cross-sectional view of the induction-heating cookingdevice according to the fourth through the sixth examples of the presentinvention.

FIG. 19 is an isometric view of light emitting means of theinduction-heating cooking device according to the fourth through thesixth examples of the present invention.

FIG. 20 is an isometric view of another light emitting means of aninduction-heating cooking device according to the fourth through thesixth examples of the present invention.

FIG. 21 is an isometric view of an induction-heating cooking deviceaccording to a seventh example of the present invention.

FIG. 22 is a partial plan view of an induction-heating cooking deviceaccording to an eighth example of the present invention.

FIG. 23 is a partial plan view of an induction-heating cooking deviceaccording to a ninth example of the present invention.

FIG. 24 shows an example of light emitting means of an induction-heatingcooking device according to a tenth example of the present invention.

FIG. 25 is a partial cross-sectional view of an induction-heatingcooking device according to an eleventh example of the presentinvention.

FIG. 26 is an external isometric view of the induction-heating cookingdevice according to the eleventh example of the present invention.

FIG. 27 is a plan view of light emitting means of the induction-heatingcooking device according to the eleventh example of the presentinvention.

FIG. 28 is a developed view of light conducting body of theinduction-heating cooking device according to the eleventh example ofthe present invention.

FIG. 29( a) is a wiring diagram of a light source of aninduction-heating cooking device according to a twelfth example of thepresent invention.

FIG. 29( b) shows a graphic pattern provided on a cooking board of theinduction-heating cooking device according to the twelfth example of thepresent invention.

FIG. 30 is an external isometric view of the induction-heating cookingdevice according to the twelfth example of the present invention.

FIG. 31 is a partial cross-sectional view of the induction-heatingcooking device according to the twelfth example of the presentinvention.

FIG. 32 shows the relationship between a light conducting body and alight source of the induction-heating cooking device according to thetwelfth example of the present invention.

FIG. 33 shows the relationship between another light conducting body anda light source of the induction-heating cooking device according to thetwelfth example of the present invention.

FIG. 34 shows an isometric view illustrating one example of a lightconducting body piece of the induction-heating cooking device accordingto the twelfth example of the present invention.

FIG. 35( a) is a wiring diagram of a light source of aninduction-heating cooking device according to a thirteenth example ofthe present invention.

FIG. 35( b) shows a graphic pattern provided on a cooking board of theinduction-heating cooking device according to the thirteenth example ofthe present invention.

FIG. 36 is an isometric view of a conventional induction-heating cookingdevice.

FIG. 37 is an isometric view of another conventional induction-heatingcooking device.

FIG. 38 is a partial cross-sectional view of still another conventionalinduction-heating cooking device.

FIG. 39 shows an example of a graphic pattern on still anotherconventional induction-heating cooking device.

FIG. 40 is a cross-sectional view of still another conventionalinduction-heating cooking device.

FIG. 41 shows the relationship between a light conducting body and alight source of still another conventional induction-heating cookingdevice.

BEST MODE FOR CARRYING OUT THE INVENTION EXAMPLE 1

Hereinafter, a first example of the present invention will be describedwith reference to FIGS. 1 through 7. FIG. 1 is a schematic view of aninduction-heating cooking device 100 according to the first example ofthe present invention. The induction-heating cooking device 100 includesa case 101 forming a main body, a cooking board 103 formed oflight-transmissive, heat-resistant glass or the like, on which a cookingcontainer 102 to be heated is to be placed, a heating coil 104 locatedbelow the cooking board 103 for heating the cooking container 102,output control means 105 for controlling an output to the heating coil104, light emitting means 106 located below the heating coil 104 andformed of a light bulb, a semiconductor device or the like for emittinga light beam, and light conducting means 107 located below the heatingcoil 104 and formed of light-transmissive glass, resin or the like forallowing the light beam from the light emitting means 106 to propagatetherethrough. The light emitting means 106 is provided to the inside ofan outer peripheral end of the light conducting means 107, so that thelight beam passes toward the outer periphery of the light conductingmeans 107 in a substantially horizontal direction as shown by arrow A1.Thus, an outer peripheral portion of the light conducting means 107 islit up. The heating coil 104 and the light emitting means 106 areconnected to the output control means 105 via a lead or the like. Thelight conducting means 107 may have an arbitrary shape when seen fromthe cooking board 103. The light conducting means 107 may have aquadrangular plate-like shape. The light conducting means 107 may have atriangular plate-like shape.

An operation of the induction-heating cooking device 100 having theabove-described structure will be described. When the induction-heatingcooking device 102 is placed on the cooking board 103 and heating isstarted, the output control means 105 outputs a signal to the heatingcoil 104 to instruct heating, and simultaneously outputs a signal to thelight emitting means 106 to instruct light emission. The generated lightbeam is propagated through the light conducting means 107 as shown byarrow A1 so as to light up the outer peripheral portion. As shown in,for example, FIGS. 2( a) through 2(c), the generated light beam istransmitted through the cooking board 103 formed of light-transmissiveglass or the like, and displays a heating state on a top surface of thecooking board 103.

As described above, the first example of the present invention lights upthe outer peripheral portion of the light conducting means 107 so as todisplay a heating state on the top surface of the cooking board 103.Accordingly, the heating state, which is conventionally visuallyseparated, is displayed in the vicinity of the cooking section. Thus,the induction-heating cooking device 100 can be used in a manner closerto using a gas cooking device.

By providing the light conducting means 107 and the light emitting means106 below the heating coil 104, the light beam can be prevented fromleaking to immediately above the light emitting means 106. When thelight conducting means 107 is formed of a resin or the like,inconveniences such as discoloring, deformation and the like areprevented from occurring due to thermal influences of heat radiation,conductance and transmission from the induction-heating cooking device100 or the like. The light emitting means 106 formed of a light bulb, asemiconductor device or the like can prevent, for example, reliabilityfrom being lowered due to malfunction or self-heat generation caused bythe influence of the strong magnetic field. Reduction in the luminousintensity which is caused by a temperature rise of the semiconductordevice or the like used for the light emitting means 106 can also beprevented.

As shown in FIGS. 2( a) through 2(c), the heating state is displayed ina circularly annular form, a semi-circularly annular form or a dot lineform in the first example. The form is not specifically limited as longas the heating state is displayed on the cooking board 103. It is notnecessary that the cooking board 103 is entirely light-transmissive.Even when a part of the cooking board 103 is non-transparent, a similareffect to that described above can be provided.

As shown in FIG. 3 as an alternative to the first example, lightconductive means 107A formed of light-transmissive glass, resin or thelike may be formed to be a disc-shaped. In this case, an opening isformed at the center of the light conductive means 107A, and lightemitting means 106 is provided in the opening. A light beam ispropagated toward an outer periphery of the light conducting means.

An operation of the induction-heating cooking device having theabove-described structure will be described. Most of point light sourcessuch as light bulbs, semiconductor devices or the like used for thelight emitting means 106 generally have a certain directivity angle. Forexample, the luminous intensity of light beam projected in the form of aflat plate parallel to the light emitting means 106 is non-uniform. Thereason is because the straight-line distance of each portion of thelight beam with respect to the parallel, flat plate is different.

However, according to the first example of the present invention, thestraight-line distance from the light emitting means 106 to the outerperipheral end of the light conducting means 107A is constant at thesame radius. Thus, display having a uniform luminous intensity can beprovided.

A diffusive material may be applied to the outer peripheral end of thelight conducting means 107A. The surface of the outer peripheral end ofthe light conducting means 107A may be processed to randomly reflectlight. A separate light receiving member may be integrally formed withor fixed on the outer peripheral end of the light conducting means 107A.In either case, a similar effect to that described above can beprovided. The number of the light emitting means 106 can be arbitrarilyset by the designer.

With reference to FIG. 4, another induction-heating cooking device 400according to the first example of the present invention will bedescribed. Identical elements previously discussed with respect to theinduction-heating cooking device 100 in FIG. 1 bear identical referencenumerals, and detailed descriptions thereof will be omitted. As shown inFIG. 4, light conductive means 107B formed of light-transmissive resinor the like is formed such that the thickness thereof is greatest at aninner portion and reduces toward the outer periphery. Reflection means108 formed of a non-transparent resin, a metal plate, a mirror or thelike is provided on a top surface, a bottom surface or both surfaces.

An operation of the induction-heating cooking device 400 having theabove-described structure will be described. As described above, most ofpoint light sources such as light bulbs, semiconductor devices or thelike used for the light emitting means 106 have a certain directivityangle. Therefore, a light incident surface 121 of the light conductingmeans 107B needs to have a thickness in accordance with the directivityangle of the light emitting means 106. When the thickness of the lightincident surface of the light conducting means 107B is thin with respectto the directivity angle of the light emitting means 106, the light beampassing outside the light conducting means 107B is lost. However, it isnot reasonable to make the entirety of the light conducting means 107Buniformly thick when the directivity angle of the light emitting means106 is wide. It is conceivable to form the light conducting means 107Bsuch that the thickness thereof reduces toward the outer periphery,i.e., in the light propagation direction. Since the light beam tends toadvance straight, the light beam passes through an inclining surfaceprovided to reduce the thickness, which results in loss of the lightbeam.

However, when the light conducting means 107B formed oflight-transmissive glass, resin or the like is formed such that thethickness thereof is greatest at an inner portion and reduces toward theouter periphery, a reasonable structure is provided while reducing theloss of the light beam at the time of incidence. By providing thereflection means 108 formed of a non-transparent resin, a metal plate, amirror or the like on the top surface, the bottom surface of bothsurfaces, a highly luminous display with a smaller loss can be provided.

With reference to FIG. 5, another induction-heating cooking device 500according to the first example of the present invention will bedescribed. Identical elements previously discussed with respect to theinduction-heating cooking device 100 in FIG. 1 bear identical referencenumerals, and detailed descriptions thereof will be omitted. As shown inFIG. 5, an outer peripheral end of light conductive means 107C formed oflight-transmissive glass, resin or the like is provided with a C cut (45degrees with respect to the light propagation direction (arrow A1)) asan illumination surface 122, such that the light beam propagated issubjected to total reflection.

An operation of the induction-heating cooking device 500 having theabove-described structure will be described. When a light beam from thelight emitting means 106 formed of a light bulb, a semiconductor deviceor the like is incident on an end of the light conducting means 107Cformed of light-transmissive glass, resin or the like, the light beampropagated through the light conducting means 107C lights up theopposite end of the light emitting means 106. The end is provided with aC cut (45 degrees with respect to the light propagation direction (arrowA1)) as the illuminating surface 122, such that the light beampropagated is subjected to total reflection. Thus, the light beam can beguided toward the cooking board 103, which is a cooking surface.

As described above, the first example of the present invention canprovide a clearer display on the top surface of the cooking board 103.

With reference to FIG. 6, another induction-heating cooking device 600according to the first example of the present invention will bedescribed. Identical elements previously discussed with respect to theinduction-heating cooking device 100 in FIG. 1 bear identical referencenumerals, and detailed descriptions thereof will be omitted. As shown inFIG. 6, an outer peripheral end of light conductive means 107C formed oflight-transmissive glass, resin or the like is provided with anillumination surface 122 (C cut). Reflection means 108 formed of anon-transparent resin, a metal plate, a mirror or the like is providedparallel to the illumination surface 122.

An operation of the induction-heating cooking device 600 having theabove-described structure will be described. When light beam propagatedthrough the light conducting means 107 is subjected to total reflectionby the illumination surface 122 (C cut (45 degrees with respect to thelight propagation direction)) provided at the outer peripheral end ofthe light conducting means 107C. However, considering the dispersionduring production or the like, it is possible that the light beam islost by the illumination surface 122 (C cut). In order to avoid this,the reflection means 108 formed of a non-transparent resin, a metalplate, a mirror or the like is provided parallel to the illuminationsurface 122 (C cut). Thus, the lost light beam is guided toward thecooking board 103, which is a cooking surface.

As described above, the first example of the present invention can guideeven the light beam, which is lost due to dispersion during productionor the like, toward the cooking board 103, which is a cooking surface,owing to the reflection means 108. Thus, a clearer display can beprovided.

In the first example, the reflection means 108 is provided. Instead, theillumination surface 122 (C cut) may be provided with a convex andconcave surface, provided with a diffusive material applied thereto, orprovided with a separate light receiving member integrally formedtherewith or fixed thereon. A similar effect to that described above canbe provided.

With reference to FIG. 7, another induction-heating cooking device 700according to the first example of the present invention will bedescribed. Identical elements previously discussed with respect to theinduction-heating cooking device 100 in FIG. 1 bear identical referencenumerals, and detailed descriptions thereof will be omitted. As shown inFIG. 7, the induction-heating cooking device 700 includes a wall section109 provided on a top surface of the illumination surface 122 (C cut),which is provided at the outer peripheral end of the light conductingmeans 107D formed of light-transmissive glass, resin or the like. Thewall section 109 extends vertically to the cooking board 103 formed oflight-transmissive, light-resistive glass or the like. Theinduction-heating cooking device 700 also includes display means 110 forrandomly reflecting or diffusing the propagated light beam on a topsurface of the wall section 109.

An operation of the induction-heating cooking device 700 having theabove-described structure will be described. The light beam guidedtoward the cooking board 103 as a result of the total reflection at theillumination surface 122 (C cut) appears to be quite below the cookingboard 103, since the light conducting means 107D is positioned below theheating coil 104. However, in this example, the wall section 109 isprovided on the top surface of the light conducting means 107 so as toguide the light beam toward the cooking board 103, and the display means110 for randomly reflecting or diffusing the light beam is provided onthe top surface of the wall section 109. Therefore, the display can beprovided at a position closer to the cooking board 103. The displaymeans 110 may have a convex and concave surface thereon so as torandomly reflect or diffuse the light beam. Alternatively, the displaymeans 110 may have a diffusive material applied thereto. Stillalternatively, the display means 110 has a separate light receivingmember integrally formed therewith or fixed thereto.

As described above, the first example of the present invention canprovide the display at a position closer to the cooking board 103, whichimproves the visual recognizability.

The top surface of the wall section 109 may be in close contact with thecooking board 103. A similar effect to that described above can beprovided. The top surface of the wall section 109 may be inclined,curved or altered in shape in an arbitrary manner by the designer. Thetop surface or a bottom surface of the cooking board 103 may be providedwith a similar convex and concave surface or processed so as to diffuselight. A similar effect to that described above can be provided.

EXAMPLE 2

With reference to FIGS. 8( a), 8(b), 9(a) and 9(b), a second example ofthe present invention will be described. FIG. 8( a) is a schematic viewof an induction-heating cooking device 800 according to the secondexample of the present invention. The induction-heating cooking device800 includes a case 201 forming a main body, a cooking board 203 formedof light-transmissive, heat-resistant glass or the like, on which acooking container 202 to be heated is to be placed, a heating coil 204located below the cooking board 203 for heating the cooking container202, light emitting means 206 located below the heating coil 204 andformed of a light bulb, a semiconductor device or the like for emittinga light beam, and light conducting means 207 located below the heatingcoil 204 and formed of light-transmissive glass, resin or the like forallowing the light beam from the light emitting means 206 to propagatetherethrough. FIG. 8( b) is a partially enlarged view of the lightconducting means 207 of the induction-heating cooking device 800. Asshown in FIG. 8( b), a border section of the light conducting means 207which receives the light beam from the light emitting means 206 isformed to have a curved portion 221 which has a concave surface facingthe light emitting means 206.

An operation of the induction-heating cooking device 800 having theabove-described structure will be described. Most of the light beamsfrom the light emitting means 206 formed of a light bulb, asemiconductor device or the like, usually expand over a certaindirectivity angle, and the range of the light beam used for display isdetermined by the directivity angle. For example, when the lightconducting means is disc-shaped as in the first example, the range fordisplay is determined by total angle (360 degrees)/directivity angle.However, few light beams have a directivity angle exceeding 90 degrees.Thus, a plurality of light emitting means 206 are required. However,when the directivity angle is large, the loss of light at the time ofincidence on the light conducting means 207 is also large. When light isnot directly used for display but light is propagated using the lightconducting means 207, the light beam is lost during propagation.Therefore, the light emitting means 206 needs to have a significantlevel of luminous intensity. In order to obtain such a high level ofluminous intensity, the directivity angle inevitably needs to be small.Usually, when a light beam passes through a border between twosubstances, the light beam is refracted with respect to the angle oflight beam incidence, and shows a negative property (angle ofrefraction) with respect to the angle at which the light beam isincident (angle of incidence). This further increases the requirednumber of light emitting means 206.

As described above, a significant number of light emitting means 206 arerequired in consideration of the loss of the light beam at the time ofincidence, the loss of the light beam during propagation, reduction inthe luminous intensity used for display, the refraction of the lightbeam, and the like. In this example, the curved surface 221 is providedwhich has a concave surface facing the light emitting means 206 at theborder portion of the light conducting means 207 (the border portion hasa property of collecting light beams when having a convex surface facingthe light emitting means 206 and dispersing the light beams when havinga concave surface facing the light emitting means 206). Owing to thecurved surface 221, even when the light emitting means 206 has a smalldirectivity angle, a highly luminous, wide range display can beprovided. The radius of the concave curved surface 221 can bearbitrarily set by the designer.

In FIG. 8( b), the light beam is propagated from an inner portion towardan outer portion of the light conducting means. As shown in FIG. 9( a),the light beam may be propagated from an outer portion to an innerportion. As shown in FIG. 9( b), the light emitting means 206 may beprovided below the light conducting means 207 such that the light beamis propagated from a lower portion toward an upper portion. In eithercase, a similar effect to that described above can be provided.

EXAMPLE 3

With reference to FIGS. 10, 11 and 12, a third example of the presentinvention will be described.

FIG. 10 is a schematic view of an induction-heating cooking device 1000according to the third example of the present invention. Theinduction-heating cooking device 1000 includes a case 301 forming a mainbody, a cooking board 303 formed of light-transmissive, heat-resistantglass or the like, on which a cooking container 302 to be heated is tobe placed, a heating coil 304 located below the cooking board 303 forheating the cooking container 302, a coil base 311 formed of aheat-resistant resin or the like, on which the heating coil 304 is to beplaced, light emitting means 306 located below the heating coil 304 andformed of a light bulb, a semiconductor device or the like for emittinga light beam, and light conducting means 307 located below the heatingcoil 304 and formed of light-transmissive glass, resin or the like forallowing the light beam from the light emitting means 306 to propagatetherethrough. The light conducting means 307 is attached by a screw 321or fixed by an adhesive to the coil base 311.

An operation of the induction-heating cooking device 1000 having theabove-described structure will be described. A heating state of theinduction-heating cooking device 1000 is displayed on a top surface ofthe cooking board 303 by the light conducting means 307. Therelationship between the heating area and the position at which theheating state is displayed by the light conducting means 307 isimportant. When the heating area is deviated with respect to theposition at which the heating state is displayed by the light conductingmeans 307, the position at which the cooking container 302 is placed isdeviated with respect to the heating area. Then, inconveniences such asreduction in the heating efficiency or non-uniformity in the heatingdistribution are expected. By attaching or fixing the light conductingmeans 307 to the coil base 309 by a screw or an adhesive, the heatingarea and the position at which the heating state is displayed by thelight conducting means 307 can be prevented from deviating with respectto each other.

As an alternative example, FIG. 11 shows an induction-heating cookingdevice 1100, in which the light conducting means 307 also acts as a coilbase on which the heating coil 304 is to be placed.

In the induction-heating cooking device 1100 shown in FIG. 11, theheating coil 304 for heating the cooking container 302 is directlyplaced on the light conducting means 307. This prevents the heating areaand the position at which the heating state is displayed by the lightconducting means 307 from deviating with respect to each other, and alsosimplifies the structure. When the light conducting means 307 is formedof a resin or the like, inconveniences such as discoloring, deformationand the like are expected to occur due to the thermal influences such asself-heat generation of the heating coil 304 or heat radiation,conductance or transmission from the cooking container 302. In order toavoid this, it is conceivable to, as shown in FIG. 12, form ribs 323 ona contact surface 322 of the light conducting means 307 which contactsthe heating coil 304. This reduces the contact area between the lightconducting means 307 and the heating coil 304, thus alleviating thethermal influences. The ribs 323 may be formed of a separate member of aheat-resistant insulating material or the like. A similar effect to thatdescribed above can be provided.

EXAMPLE 4

With reference to FIGS. 13, 14(a) and 14(b), a fourth example of thepresent invention will be described. FIG. 13 is a schematic view of aninduction-heating cooking device 1300 according to the fourth example ofthe present invention. The induction-heating cooking device 1300includes a case 401 forming a main body, a cooking board 403 formed oflight-transmissive, heat-resistant glass or the like, on which a cookingcontainer 402 to be heated is to be placed, a heating coil 404 locatedbelow the cooking board 403 for heating the cooking container 402, acoil base 411 on which the heating coil 404 is to be placed, lightemitting means 406 located below the heating coil 404 and formed of alight bulb, a semiconductor device or the like for emitting a lightbeam, and light conducting means 407 located below the heating coil 404and formed of light-transmissive glass, resin or the like for allowingthe light beam from the light emitting means 406 to propagatetherethrough. The light emitting means 406 is attached by a screw 421 orfixed by an adhesive to the light conducting means 407.

An operation of the induction-heating cooking device 1300 having theabove-described structure will be described. As described in the firstexample, most of the light beams emitted by the light emitting means 406formed of a light bulb, a semiconductor device or the like, usuallyexpand over a certain directivity angle. The following inconveniencesare expected. The light beam is lost at the time of incidence due to thepositional deviation between the light emitting means 406 and the lightconducting means 407. As a result, the display is difficult to seethrough the cooking board 403 due to the insufficient amount of light,or the display is non-uniform due to the non-uniform luminous intensity.By screwing or fixing the light emitting means 406 to the lightconducting means 407 by a screw or an adhesive, the position ofincidence of the light beam emitted by the light emitting means 406 canbe restricted. Therefore, the loss of the light beam at the time ofincidence can be minimized.

In FIG. 13, the light emitting means 406 is attached to by a screw orfits in the light conducting means 407 parallel to the light conductingmeans 407. This is easy in terms of production. As shown in FIG. 14( a),a substrate 422 of the light emitting means 406 may be parallel to thelight conducting means 407. Only the light bulb, the semiconductordevice or the like is provided in the same direction as the light beampropagation direction. As shown in FIG. 14( b), the substrate 422 of thelight emitting means 406 may be vertical to the light conducting means407. The light bulb, the semiconductor device or the like is providedvertical to the light beam propagation direction. These structures canfurther reduced the loss of the light beam at the time of incidence.

EXAMPLE 5

With reference to FIG. 15, a fifth example of the present invention willbe described. FIG. 15 is a schematic view of an induction-heatingcooking device 1500 according to the fifth example of the presentinvention. The induction-heating cooking device 1500 includes a case 501forming a main body, a cooking board 503 formed of light-transmissive,heat-resistant glass or the like, on which a cooking container 502 to beheated is to be placed, a heating coil 504 located below the cookingboard 503 for heating the cooking container 502, output control means505 for controlling an output from the heating coil 504, ventilationmeans 512 formed of a fan or the like for cooling the output controlmeans 505, a duct 513 forming a path for sending air to the outputcontrol means 505, light emitting means 506 located below the heatingcoil 504 and formed of a light bulb, a semiconductor device or the likefor emitting a light beam, and light conducting means 507 located belowthe heating coil 504 and formed of light-transmissive glass, resin orthe like for allowing the light beam from the light emitting means 506to propagate therethrough. The induction-heating cooking device 1500 isstructured such that the light emitting means 506 and the lightconducting means 507 are cooled after the output control means 505 iscooled.

An operation of the induction-heating cooking device 1500 having theabove-described structure will be described. Cooling air generated bythe ventilation means 512 cools the output control means 505 via theduct 513. As shown in FIG. 15, an outlet section 513A of the duct 513 isshaped such that the air is directed toward the light emitting means 506and the light conducting means 507. Thus, the air cools the outputcontrol means 505, and after that cools the light emitting means 506 andflows between the light conducting means 507 and the heating coil 504toward the cooking board 503. Therefore, the luminous intensity of thesemiconductor device used for the light emitting means 506 can beprevented from being lowered, and inconveniences such as discoloring,deformation and the like of the resin used for the light conductingmeans 507 can be prevented from occurring due to the thermal influenceof radiation, conductance or transmission from the cooking container 502or the like, or the thermal influence of self-heat generation of theheating coil 504.

EXAMPLE 6

With reference to FIG. 16, a sixth example of the present invention willbe described. FIG. 16 shows light emitting means 606 formed of a lightbulb, a semiconductor device or the like for emitting a light beam, andlight conducting means 607 formed of light-transmissive glass, resin orthe like for allowing the light beam from the light emitting means 606to propagate therethrough. The light conducting means 607 includes aplurality of light conducting blocks 622 corresponding to a plurality oflight emitting means 606. The light conducting blocks 622 are obtainedby forming the light conducting means 607 into blocks.

An operation of the induction-heating cooking device including the lightemitting means 606 and the light conducting means 607 having theabove-described structure will be described. The light conducting means607 includes light conducting blocks 622 which are formed into blocks inaccordance with the directivity angle of the light emitting means 606.When a plurality of light conducting blocks 622 are combined, a space621 can be formed as shown in FIG. 16. As described in the fifthexample, the space 621 is very advantageous for cooling and improves thecooling ability of the induction-heating cooking device.

The light conducting means 607 is provided in the form of blocks.Therefore, even when a part of the light conducting means 607malfunctions, only the light conducting block which malfunctions needsto be replaced. Thus, the light conducting means 607 can be repairedrapidly and easily.

EXAMPLE 7

In seventh through ninth examples of the present invention, a so-calleddual heating cooking stove including two heating sections which operateby induction heating will be described. FIG. 17 is an isometric view ofan induction-heating cooking device 1700 according to the sevenththrough ninth examples of the present invention, and FIG. 18 is across-sectional view of the induction-heating cooking device 1700.

As shown in FIGS. 17 and 18, the induction-heating cooking device 1700includes a case 2001 forming a main body, a light-transmissive cookingboard 2002 provided on a top surface of the case 2001, heating sections2003 for heating a cooking container provided thereon by inductionheating, heating coils 2004 provided below the cooking board 2002 incorrespondence with the heating sections 2003 for heating the heatingsections 2003, a control section 2005 for controlling the contents ofthe display of the heating coil 2004, a temperature sensor 2006 forsensing the temperature of the heating sections 2003, light emittingmeans 2007 for displaying a use state on the cooking board 2002, a powerswitch 2008 for turning on/off the power, a power display section 2009for displaying the on/off state of the power switch 2008, an outputsetting section 2010 for setting the output, an output display section2011 for displaying the setting state of the output, and second outputdisplay sections 2012 provided on a front area of the cooking board2002. Reference numeral 2013 represents a radiation heater used forheating an aluminum pan or a copper pan which cannot be heated byinduction heating. Hereinafter, the seventh example will be specificallydescribed.

In the seventh example, the display allows the user to visuallyrecognize that the heating section 2003 is turned on at the same timewhen the power is turned on. In the seventh example, graphic patternsare used for display. With the above-described structure, when the powerswitch 2008 is turned on, the power display section 2009 is lit up. Atthe same time, the light emitting means 2007 emits light. The light istransmitted through the light-transmissive cooking board 2002 anddisplays a graphic pattern, in the vicinity of the heating sections2003, which indicates that the power has been turned on. The graphicpattern may be any thing which is easy to be visually recognized, andthus may be a rod-like pattern having a size of about the radius of theheating coil 2004. A graphic pattern which partially or entirely coversa periphery of the heating coil 2004, for example, a part or an entiretyof a circle, a quadrangle or other polygons are sufficiently large to beeasily recognized visually. Such a graphic pattern also clearly showsthe position at which the cooking container is to be placed, and thusimproves the ease of use.

The graphic patterns may be displayed by lighting up or by blinking.Various colors including red, blue and the like may be used. When thereare two heating sections 2003 using induction heating as in the seventhexample, the states of the heating sections 2003 may be displayed indifferent forms. For example, the state of the heating section forfrying may be displayed by blinking, and the state of the heatingsection for pans may be displayed by lighting-up. The color may bechanged in accordance with the output of the heating section.

In the seventh example, the light-transmissive cooking board 2002 isused. It is not necessary that the cooking board 2002 is entirelylight-transmissive. A portion required for displaying a graphic patternmay be light-transmissive, and the rest may be non-light transmissive.

Next, the light emitting means 2007 will be described. For displaying arod-shaped graphic pattern, rod-shaped light emitting bodies, lightbulbs, or semiconductor devices such as LEDs may be arranged linearly.For displaying a graphic pattern partially or entirely covering theheating section 2003, annular light emitting bodies, light bulbs orsemiconductor devices may be arranged, but this may undesirably raisethe cost. It is practical to use a light conducting plate as the lightemitting means 2007.

FIG. 19 shows the light emitting means 2007 including a donut-shapedlight conducting body 2014 and a light source 2015 provided at thecenter thereof. The light source 2015 is formed of a light bulb or asemiconductor device. When the power switch 2008 is turned on, the lightsource 2015 at the center is lit up. The light is guided by the lightconducting body 2014 to light up the periphery of the light conductingbody 2014. The light at the periphery displays a graphic pattern, acircle in the seventh example, on the cooking board 2002. Where thediameter of the light conducting body 2014 is slightly greater than thediameter of the heating coil 2004, a circle can be displayed around theheating section 2003.

FIG. 20 shows a fan-shaped light conducting body 2016A, which isobtained by dividing the light conducting body 2014 shown in FIG. 19.The fan-shaped light conducting body 2016A and a light source 2017provided at the pivotal point thereof are provided as one block. Bycombining such blocks, a semi-circular pattern or other graphic patternscan be displayed.

In the above, the light emitting means 2007 which is circular or havinga similar shape is described. Various other shapes such as quadrangularshapes may be obtained by combining a light conducting plate and a lightsource.

As described above, the seventh example allows the user to easilyconfirm whether the power is on or not. However, the user sometimesturns the power on but does not use the induction-heating cookingdevice. In this case, the following method can be used.

When the output setting section 2010 is not operated for a prescribedperiod of time, for example, 5 minutes, after the power switch 2008 isturned on, the control section 2005 automatically turns off the powerswitch 2008.

In the structure having two heating sections, when the power switch 2008is turned on, graphic patterns for both heating sections are displayed.When only one heating section is used and the other heating section iskept unused, the display for the heating section which is not used isturned off after a prescribed period of time. Since the display for theheating section which is used is on, the user can recognize that thepower switch for the other heating section is also on.

Alternatively, in the structure having two heating sections, theinduction-heating cooking device may be formed such that only thegraphic pattern for one heating section is displayed when the powerswitch 2008 is turned on. In this case also, since the display for oneheating section is on, the user can recognize that the power for theother heating section is on.

The induction-heating cooking device may also be formed such that whenthe power switch 2008 is turned on, no graphic pattern for the heatingsections is displayed. The graphic pattern is only displayed when theoutput setting section (switch for each heating section) 2010 of theheating section to be used is operated. In this case, the heatingsection in use can be clearly shown.

These techniques save power.

As described above, the seventh example allows the user to easilyconfirm visually whether the power is turned on or not. This eliminatesthe trouble of confirming the on/off state of the power.

EXAMPLE 8

The eighth example of the present invention regards a process after theseventh example. When the output setting section 2010 sets an output forcooking using the induction-heating cooking device 1700 shown in FIG.17, a different graphic pattern is shown on the cooking board 2002 fromthe graphic pattern used for indicating that the power is on.

When the power switch 2008 is turned on and then the output is set toput the induction-heating cooking device 1700 to a heating state, thedisplay on the cooking board 2002 is changed in accordance with the usestate. Specifically, where a circle is displayed on the cooking board2002, the circle blinks when the power switch 2008 is turned on, and thecircle lights up when heating is started. In this manner, the user caneasily confirm visually that the power is turned on and that heating isstarted.

The state may be identified by the color of the display. For example,the display is in blue when the power is turned on, and the color ischanged to red when heating is started.

The state may be identified by the darkness of the color of the display.For example, the display is in pale red when the power is turned on, andthe color is changed to dark red when heating is started. The displaymay be changed in accordance with the use state by lighting-up/blinking,colors, and color combinations.

Various use states may be represented by various combinations. Forexample, the pattern is lit up in blue when the power is turned on, thepattern is lit up in red when heating is started, and the pattern blinksin red when heating is completed.

Such different colors may be realized by using a set of light sourcesemitting different colors of light, which is controlled by the controlsection 2005. Alternatively, filters may be used when appropriate. Thedarkness of the color can be easily changed by changing the output tothe light source using the control section 2005.

EXAMPLE 9

The ninth example of the present invention regards a method of utilizingthe second output display section 2012 provided on a front area of thecooking board 2002. When the power switch 2008 is turned on, the outputdisplay section 2012 blinks. When the output is set, the output displaysection 2012 is lit up. The second output display section is usuallydivided into several sections in order to represent the magnitude of theoutput. The output display section 2012 is lit up over a wide range atthe maximum output, but over a narrow range at the minimum output. Inorder to allow the user to easily confirm the range visually even at theminimum output, the size of the output display section 2012 ispreferably slightly larger than actually necessary. The blinking can beperformed at the maximum output in order to allow the user to easilyconfirm the state. When the display is blinking, the display shouldcorrespond to the maximum output in order to allow the user to easilyconfirm.

As in the eighth example, where the state where the heating is completedand the power is still on is represented by lighting up a specificcolor, the color of light may be blinked to show the proceeding state ofcooking. As described above, various combinations may be used to providevarious forms of display.

As described above, the ninth example allows the user to easily confirmthe proceeding state of cooking.

In the seventh through ninth examples, there are two induction-heatingsections. The seventh through ninth examples are applicable to whenthere is only one induction-heating section or there are three or moreinduction-heating sections. The embodiments described in the sevenththrough ninth examples can be easily carried out.

EXAMPLE 10

With reference to a figure, a tenth example of the present inventionwill be described.

The cooking board used in the present invention may belight-transmissive or non-light transmissive. In the case where thecooking board is non-light transmissive, a portion of the cooking boardcorresponding to the graphic pattern needs to be light-transmissive.This can be achieved by applying a blackish inorganic paint to a bottomsurface of the cooking board formed of light-transmissive glass exceptfor the portion which needs to be light-transmissive. In the tenthexample, a light-transmissive cooking board is used.

In the tenth example, a plurality of heating coils having differentrated outputs are used. In this example, two heating coils having ratedoutputs of 2 kW and 3 kW are used. It is assumed that the 2 kW heatingcoil is provided on the left, and the 3 kW heating coil is provided onthe right.

The induction-heating cooking device in the tenth example is basicallysimilar to the conventional induction-heating cooking device 3700 shownin FIG. 37, except for the method for displaying the state of theheating sections on the cooking board. Accordingly, identical elementsto those in FIG. 37 bear identical reference numerals thereto, anddetailed descriptions thereof will be omitted.

The display on the cooking board is provided by the light emitted by thelight emitting means located below the cooking board and seen from abovethe cooking board, which is light-transmissive (i.e., the display meansis provided on the cooking board). The graphic pattern substantiallymatches the structure of the light emitting means. The tenth example isprovided in order to clearly describe the method for display, and thusthe light emitting means is only described generally.

FIG. 21 is an isometric view of an induction-heating cooking device 2100according to the tenth example of the present invention. In FIG. 21, aheating section 3006 on the left corresponds to the 2 kW heating coil. Aheating section 3007 on the right corresponds to the 3 kW heating coil.In the tenth example, the different rated outputs are represented by thesize of the graphic patterns, i.e., the circles surrounding the heatingsections. The radius of the circle corresponding to the rated output of3 kW is larger than the radius of the circle corresponding to the ratedoutput of 2 kW. Thus, it is easily recognized visually which heatingsection has a larger output.

In the tenth example, a circle is used as the graphic pattern.Alternatively, a polygon such as a quadrangle surrounding the entiretyof the heating section, or a part of a circle or a polygon may be used.

The difference in size of the graphic patterns may be sufficiently largeto represent the difference in rated output. Therefore, the graphicpatterns need not be sufficiently large to surround the heating section.A graphic pattern which is sufficiently large to surround the heatingsection is preferable since such a large graphic pattern allows thedifference in rated output to be recognized even after the cookingcontainer is placed on the cooking board, while the cooking container isheated or during cooking.

In this example, the graphic patterns surround the heating sections.Since this undesirably raises the cost, the difference may berepresented by the difference in lengths of lines. Alternatively, lightbulbs of different sizes may be used so as to provide a dot display.However, lines or dots makes it more difficult to recognize thedifference than circles or the like surrounding the heating sections.

EXAMPLE 11

FIG. 22 is a plan view illustrating heating sections 3008 and 3009,which are main parts of an induction-heating cooking device according toan eleventh example of the present invention. In FIG. 22, the width ofthe circumferential portion of the circle for the heating section 3008corresponding to the heating coil having a rated output of 2 kW issmaller than the width of the circumferential portion of the circle forthe heating section 3009 corresponding to the heating coil having arated output of 3 kW.

As in the tenth example, the graphic pattern is not limited to a circle.In the case where lines are used for display, the difference in width ofthe lines allows the user to recognize the difference. In the case wheredots are used for display, the difference in size of the dots allows theuser to recognize the difference.

The concept of displaying the graphic patterns of the tenth example maybe combined with the concept of displaying the graphic patterns of theeleventh example.

EXAMPLE 12

FIG. 23 is a plan view illustrating heating sections 3010 and 3011,which are main parts of an induction-heating cooking device according toa twelfth example of the present invention. In FIG. 23, the heatingsection 3010 corresponding to a rated output of 2 kW is represented byone circle, and the heating section 3011 corresponding to a rated outputof 3 kW is represented by two circles. This allows the user to recognizethe difference in output at a glance. In the case where the heatingsections are surrounded by polygons, one of the heating sections may besurrounded by one polygon and the other may be surrounded by polygonswhich are similar to each other and have different sizes. The similarpolygons are provided concentrically. When lines or dots are used fordisplay, the user can recognize the difference by the difference in thenumber of lines or dots.

The concept of displaying the graphic patterns of the twelfth examplemay be combined with the concept of displaying the graphic patterns ofthe tenth and/or the eleventh example.

EXAMPLE 13

In the tenth through twelfth examples above, the difference in ratedoutput is represented by the difference in the graphic pattern.

In a thirteenth example, the difference in rated output is representedby the difference in color of the graphic pattern. For example, theheating sections corresponding to different rated outputs are displayedby circles of the same size. The heating section having a rated outputof 2 kW is represented by blue, and the heating section having a ratedoutput of 3 kW is represented by red. Different levels of darkness ofthe same color may also be used. For example, the heating section havinga rated output of 2 kW is represented by pale red, and the heatingsection having a rated output of 3 kW is represented by dark red.

The display can be colored by using a color light source obtained bycoloring an outer cover of a rod-shaped heating element such as a lightbulb or a fluorescent lamp, or by using a filter. Thus, desired colorsor desired levels of darkness can be selected.

A pattern surrounding a heating section such as a circle can be coloredas shown in FIG. 24. A color light source, obtained by coloring an outercover of annular light emitting means such as a fluorescent lamp, isprovided as light emitting means 3013 at the center of a donut-shapedlight conducting plate 3012. The light emitted by the light emittingmeans 3013 is guided by the light conducting plate 3012 so as to lightup the periphery of the light conducting plate 3012 in an annular form.Thus, a circle can be displayed on the cooking board. At this point, acolor light source can be used as the light source. Alternatively, acolor light conducting plate may be used as the light conducting plate3012. Still alternatively, a lighting paint which is lit up whenirradiated with light is applied to the bottom surface of the cookingboard in advance, and the lighting paint is lit up.

EXAMPLE 14

In the tenth through thirteenth examples, a graphic pattern is displayedfor each of the heating sections having different rated outputs. In afourteenth example, where there are two induction-heating sections, thestate of one of the sections is displayed. The graphic pattern can bedisplayed in accordance with the tenth through thirteenth examples.

As described in the tenth through fourteenth examples, the difference inrated output can be represented by various shapes or colors of graphicpatterns. The patterns are not limited to those described in the tenththrough fourteenth examples. The shape of the pattern can beappropriately altered by combinations of dots, straight lines, circles,polygons, parts of circles or polygons, and colors. For example, whereasa heating section having a rated output of 2 kW is represented by acircle, a heating section having a rated output of 3 kW may berepresented by a circle having a larger radius, a wider circumferentialportion and a different color. In this case, an inner portion of theheating section may be used as a plane, and the difference can berepresented by the difference in light intensity of planar emission.

As described above, the present invention provides light emitting meansbelow a cooking board and displays the light obtained by the lightemitting means on the cooking board. There are other methods fordisplaying a graphic pattern on the cooking board and representing thedifference. In the case where a graphic pattern is provided on thebottom surface of the cooking board, the user looks at reflected lightof the light incident from the top surface of the cooking board. Suchreflected light is undesirably difficult to see due to the largethickness of the cooking board. When a graphic pattern is provided onthe top surface of the cooking board, abrasion caused by the frictionwith the cooking container needs to be considered.

In the above examples, there are two heating sections. There can be morethan two heating sections. The effect of the present invention increasesas the number of the heating sections is greater and there is a largerdifference among rated outputs of the heating sections.

In the above, the rated outputs are 2 kW and 3 kW. The present inventionis not limited to such rated outputs. The rated outputs maybe smaller orlarger. A heating section having a larger output may be provided on theleft and a heating section having a smaller output may be provided onthe right.

An induction-heating cooking device generally includes temperaturesensing means and control means. Utilizing these, the graphic patternaccording to the present invention may be lit up during cooking andblinked after cooking until the temperature of the cooking board islowered down to a safe level. Functions such as “no pan”, “frying” andthe like may be represented by different forms of display.

EXAMPLE 14

With reference to figures a fourteenth example of the present inventionwill be described.

An outer peripheral portion of a heating coil in the sense of thepresent invention refers the light conducting body which is outside theheating coil, but does not refer to the position in the heightdirection. In the fourteenth example, the light conducting body will bedescribed as being provided below the heating coil.

FIG. 26 is an isometric view of an induction-heating cooking device 2500according to the fourteenth example of the present invention. As shownin FIG. 25, a light-transmissive cooking board 4006 is provided on a topsurface of a main body case 4005. The cooking board 4006 has a heatingsection 4007 for heating a pan by induction heating so as to cook foodand a radiation heater 4008 for cooking using a pan which cannot be usedfor induction heating. A roaster 4009 and an operation section 4010 areprovided on a front side surface of the main body case 4005.

FIG. 25 is a partial cross-sectional view illustrating a cross-sectiontaken along one of the two directions. In FIG. 25, a cooking pan 4011 isplaced on the heating section 4007 (FIG. 26) of the cooking board 4006.In order to heat the cooking pan 4011, a heating coil 4012 is providedat a position below the cooking board 4006 corresponding to the heatingsection 4007 (FIG. 26), i.e., a cooking pan. A light conducting body4013 is provided below the heating coil 4012. By forming the lightconducting body 4013 so as to have a size substantially covering theentirety of the heating coil 4012 including an outer peripheral portionthereof, the light from the light conducting body 4013 reaches thecooking board 4006 without being shielded by the heating coil 4012.Thus, the area of the heating section 4007 can be clearly displayed onthe cooking board 4006. As the light conducting body 4013, a materialhaving a superb light transmittance such as an acrylic resin, apolycarbonate resin or glass is used. Reference numeral 4014 representsa light source formed of a light bulb or an LED (semiconductor lightemitting device). Light emitted by the light source 4014 is propagatedthrough the light conducting body 4013. Reference numeral 4015represents a control section for, for example, adjusting the heatingpower for cooking or controlling the light source 4014 to blink.

FIG. 27 is a plan view illustrating a structure of light emitting meansincluding a light conducting body and a light source as one set, whichis one feature of the present invention.

In FIG. 27, the light conducting body 4013 is circular and donut-shapedin correspondence with the circular heating coil 4012 (FIG. 25). Theinner diameter of the light conducting body 4013 is slightly larger thanthe outer diameter of the heating coil 4012. The cross-section in adirection vertical to the optical path of the light conducting body 4013may be circular, quadrangular or of a similar shape. The lightconducting body 4013 is generally easily obtained by resin molding.

A light source chamber 4016 is provided at a position of the lightconducting body 4013 at which light is incident. In the fourteenthexample, one light bulb is provided as a light source 4014 in the lightsource chamber 4016. The light source chamber 4016 is surrounded by areflective plate so as to prevent light from being released to adirection other than toward the light conducting body 4013. Lightemitted by the light source 4014 advances straight or propagates whilebeing reflected in repetition inside the light conducting body 4013 asshown by arrow 4021. During the propagation, the light is releasedtoward the cooking board 4006, and the intensity of the light isattenuated. In this manner, the light is released toward the cookingboard 4006 while propagating in the light conducting body 4013.Therefore, a graphic pattern having the same shape as that of the topsurface of the light conducting body 4013 is displayed on the cookingboard 4006. In FIG. 27, a circle is displayed.

When the light is released in a direction other than toward the cookingboard 4006 during the propagation, the intensity of the light isattenuated. In order to restrict this, the light conducting body 4013 isprovided with a reflective layer in a portion other than the portionthrough which the light is released toward the cooking board 4006. Thereflective layer may be formed of a metal foil or plate formed ofaluminum or stainless steel, or may be formed by vapor deposition orsputtering of a metal material or a metal oxide material. Alternatively,the reflective layer may be formed by painting or chemical methods.Regardless of the technique, provision of the reflective layer canrestrict the release of the light in directions other than toward thecooking board 4006 and thus can restrict the attenuation of light.

FIG. 28 is a developed view of the light conducting body 4013 obtainedby resin molding. FIG. 28 illustrates the structure of the lightconducting body for uniformizing the light released toward the cookingboard 4006. For example, FIG. 27 shows the light conducting body 4013obtained by rolling the light conducting body 4013 having a shape shownin FIG. 28 into a circle. As shown in FIG. 28, the light conducting body4013 is horizontal in an upper portion 4013 a from which light isreleased, and is inclined in a lower portion 4013 b for reflecting thelight. As shown in FIG. 28, the distance between the lower portion 4013b for reflecting light and the upper portion 4013 a for releasing lightbecomes gradually shorter as it becomes further from the light source4014. Thus, light incident at point p which is not much distanced fromthe upper portion 4013 a encounters, and is reflected by, the lowerportion 4013 b at a position 4022 which is away from the light source4014 by distance L2. Then, the light is directed toward the upperportion 4013 a. Light which is incident at point q which is moredistanced from the upper portion 4013 a encounters, and is reflected by,the lower portion 4013 b at a position 4023 which is away from the lightsource 4014 by distance L1. Then, the light is directed toward the upperportion 4013 a. In this manner, the light can be uniformly released fromthe upper portion 4013 a of the light conducting body 4013. A graphicpattern having a uniform light intensity can be provided on the cookingboard 4006.

Next, a method for providing a reflective layer on the lower portion4013 b of the light conducting body will be described. A randomreflective layer, which is a type of reflective layer, is provided bymechanically polishing the surface of the lower portion 4013 b so as toform convex and concave portions. Alternatively, chemical etching may beused. When etching does not provide sufficient convex and concaveportions, masking can be used in combination. While the light conductingbody 4013 is formed by resin molding, the lower portion 4013 b may beformed so as to have fine convex and concave portions. The convex andconcave portions may be provided by causing the same type or a differenttype of substance to adhere to the surface of the lower portion 4013 bby spraying or the like. By causing metal powder or the like to adhereto the convex and concave surface obtained in this manner, a randomreflective layer is provided. When light is incident on the randomreflective layer, the light is diffused and reflected in variousdirections. Thus, uniformity in light is easily obtained.

A mirror reflective layer can be formed as follows, for example. A metalpowder layer is provided on the lower portion 4013 b of the lightconducting body by vapor deposition, sputtering or painting, asdescribed above. Alternatively, a metal foil or a plate is bonded to thelower portion 4013 b of the light conducting body. When the lowerportion 4013 b is inclined, the resultant mirror reflective layer isespecially effective for uniformizing the light from the upper portion4013 a.

When the lower portion 4013 b is inclined, a great number of continuoussawtooth-shaped prisms may be provided on a surface of the lower portion4013 b during resin molding. The incident light is reflected by theprisms, and thus the light is released from the upper portion 4013 a. Inthis manner also, uniformity in light is obtained.

A light reflective layer may also be provided by covering the lightconducting body 4013 with a substance having a smaller refractive indexthan that of light. Then, the light is subjected to total reflection atthe interface of the light conducting body 4013 and the substance.

In the fourteenth example, light incident from the light source 4014 iscaused to light up the entirety of the light conducting body 4013. Agraphic pattern having a dark portion and a pale portion can bedisplayed on the cooking board 4006 as follows. In order to partiallychange the reflectance of the lower portion 4013 b of the lightconducting body 4013, the roughness of the lower portion 4013 b ispartially changed. Alternatively, in the case where the lower portion4013 b is inclined, the gradient is partially changed so as to partiallychange the reflectance.

In the case where the outer periphery of the heating coil is too long,the intensity of the light emitted by the light source may undesirablybe excessively reduced at a position far from the light source if thereis only one light source. In this case, a light source and asemicircular light conducting body are formed as one unit, and two suchunits may be used. The number of units may be increased as necessary.

In the fourteenth example described above, the light conducting body hasa circular outer appearance. As described above, the light conductingbody maybe quadrangular, circular or of a similar shape. The lightconducting body is preferably circular for the following reason. Sincethe heating coil is usually circular, a circular light conducting bodyclarifies the position of the heating coil, i.e., the position of theheating section. In addition, a circular light conducting body is highlystable.

In the above description, a graphic pattern is provided over a positioncorresponding to the entire periphery of the heating coil. Whennecessary, a graphic pattern is provided over a position correspondingto a half or a part of the entire periphery of the heating coil.

As described above, the fourteenth example realizes a clear, continuousgraphic pattern provided over the entirety of the cooking board, insteadof dots or lines. Since only a minimum amount of light sources isrequired, the production cost can be low.

EXAMPLE 15

With reference to figures, a fifteenth example of the present inventionwill be described.

FIG. 30 is an isometric view of an induction-heating cooking device 3000used in the fifteenth example of the present invention. As shown in FIG.30, a light-transmissive cooking board 5007 is provided on a top surfaceof a main body case 5006. The cooking board 5007 has a heating section5008 for heating a pan by induction heating so as to cook food and aradiation heater 5009 for cooking using a pan which cannot be used forinduction heating. A roaster 5010 and an operation section 5011 areprovided on a front side surface of the main body case 5006.

FIG. 31 is a partial cross-sectional view illustrating a cross-sectiontaken along one of the two directions. In FIG. 31, a cooking pan 5012 isplaced on the heating section 5008 (FIG. 30) of the cooking board 5007.In order to heat the cooking pan 5012, a heating coil 5013 is providedat a position below the cooking board 5007 corresponding to the heatingsection 5008, i.e., a cooking pan. A light conducting body 5014 isprovided below the heating coil 5013. By forming the light conductingbody 5014 so as to have a size substantially covering the entirety ofthe heating coil 5013 including an outer peripheral portion thereof, thelight from the light conducting body 5014 reaches the cooking board 5007without being shielded by the heating coil 5013. Thus, the area of theheating section 5008 can be clearly displayed on the cooking board 5007.As the light conducting body 5014, a material having a superb lighttransmittance such as an acrylic resin, a polycarbonate resin or glassis used. Reference numeral 5015 represents alight source formed of alight bulb or an LED (semiconductor light emitting device). Lightemitted by the light source 5015 is propagated through the lightconducting body 5014 and is directed toward the cooking board 5007 atthe outer peripheral portion of the light conducting body 5014.Reference numeral 5016 represents a control section for, for example,adjusting the heating power for cooking or controlling the light source5015 to blink.

FIG. 29( a) is a wiring diagram illustrating a two-system light sourcestructure as one example of a multiple-system light source structure,which is one feature of the present invention. The two-system lightsource structure shown in FIG. 29( a) includes a system 5018A includingsix light sources 5015 a and a power supply 5017 a therefor, and asystem 5018B including six light sources 5015 b and a power supply 5017b therefor. The power supplies for the light sources may be DC or ACpower supplies. FIG. 29( b) shows exemplary graphic patterns provided onthe cooking board 5007 respectively by the light sources 5015 a and thelight sources 5015 b. A graphic pattern 5019 a is provided by the system5018A, and a graphic pattern 5019 b is provided by the system 5018B. InFIG. 29( b), a clear border 5032 is provided between the system 5018Aand the system 5018B. The systems 5018A and 5018B may be designed so asto have the clear border 5032 therebetween or overlap each other.

In FIG. 29, when, for example, one of the light sources 5015 amalfunctions, the system 5018A is turned off. In this state, the usercan recognize that the system 5018A malfunctions. Since the system 5018Bis lit up, the user can visually recognize that the induction-heatingcooking device is now heated. In the structure in which the system 5018Aand the system 5018B are blinking simultaneously or alternately, theuser can visually recognize more easily that the induction-heatingcooking device is now heated.

With reference to FIG. 32, the relationship between the light conductingbody 5014 and the light source 5015 will be described. In FIG. 32, theconducting body 5014 is circularly annular, and a plurality of lightsources 5015 are provided in a circularly annular manner at the centerof the conducting body 5014. In FIG. 32, 12 light sources 5015 are used.Six light sources on the left are connected in series so as to form thesystem 5018A, and the six light sources on the right are connected inseries so as to form the system 5018B. Each system is provided as ablock. By providing a plurality of light sources in this manner, lightis provided uniformly from the outer periphery of the circularly annularlight conducting body 5014. Thus, a circular graphic pattern isdisplayed on the cooking board.

The method of connection of lead sections 5020 of the light sources 5014is not specifically limited. In FIG. 32, the lead sections 5020 of thelight sources are arranged radially from the center of the circle. Thisis for reducing the malfunction and heat generation caused by a magneticfield at the time of induction heating. The lead sections 5020 of thelight sources 5015 may be leads or patterns on a substrate.

FIG. 33 illustrates another example showing the relationship between thelight conducting body 5014 and the light sources 5015. In FIG. 33, thelight conducting body 5014 is divided into a plurality of lightconducting body pieces 5014 a. A light conducting body piece 5014 a andat least two light sources 5015 are formed as one block. A plurality ofsuch blocks are assembled. In FIG. 33, a circularly annular structure isformed of six blocks. By combining the light conducting body piece 5014a and the light sources 5015 in this manner, various graphic pattern canbe obtained. In FIG. 33, 12 light sources 5015 are used, and areconnected in the same manner as in FIG. 32. Lead sections 5021 of thelight sources 5015 are arranged radially from the center of the circle.The example in FIG. 33 is different from the example shown in FIG. 32 inthat the leads sections 5021 of the light sources 5015 are twisted inFIG. 33. By this arrangement, the influence of the magnetic field canfurther be reduced as compared to the example in FIG. 32. The leadsections 5021 of the light sources 5015 may be leads or patterns on asubstrate.

Providing the lead sections radially, or twisting and providing the leadsections radially, is not related to the shape of the light conductingbody. For example, the lead sections maybe twisted in FIG. 32. The leadsections are arranged in such manners for the purpose of preventing theinfluence of the magnetic field at the time of induction heating asdescribed above. For this purpose, such arrangements may be used for anyof the induction-heating cooking devices.

In FIGS. 33 and 34, the light conducting body 5014 is circularlyannular. The present invention is not limited to this. The lightconducting body 5014 may assume any shape as long as it is annular(substantially ring-shaped).

FIG. 34 shows still another example of the light conducting body (5014b). The light conducting body 5014 b has a wall 5022 around the outerperiphery thereof, which extends vertically to the cooking board 5007(FIG. 30). This can increase the intensity of light directed to thecooking board 5007.

EXAMPLE 16

With reference to FIGS. 35( a) and 35(b), a sixteenth example of thepresent invention will be described. The sixteenth example is differentfrom the fifteenth example in the manner of connecting a plurality oflight sources. The other parts of the sixteenth example are the same asthose of the fifteenth example and thus will not be described.

FIG. 35( a) is a wiring diagram of a plurality of light sources in thesixteenth example. Unlike in the fifteenth example, the light sources5015 a of the system 5018A and the light sources 5015 b of the system5018B are alternately provided, and both systems use six light sources.FIG. 35( b) shows exemplary graphic patterns provided on the cookingboard 5007 respectively by the light sources 5015 a and the lightsources 5015 b. A graphic pattern 5023 a on the left in FIG. 35( b) isprovided by a light source section 5022 a on the left of FIG. 35( a),and a graphic pattern 5023 b on the right of FIG. 35( b) is provided bya light source section 5022 b on the right of FIG. 35( a). The graphicpatterns 5023 a and 5023 b may be designed so as to have the clearborder therebetween or overlap each other.

In FIGS. 35( a) and 35(b), when, for example, one of the light sources5015 a malfunctions, the system 5018A is turned off. In this state, theuser can recognize that a malfunction occurs since the color of thedisplay becomes lighter. Since the system 5018B is lit up, the user canvisually recognize that the induction-heating cooking device is nowheated although the display is lighter.

In the structure in which the system 5018A and the system 5018B areblinking simultaneously or alternately, the user can visually recognizemore easily that the induction-heating cooking device is now heated. Byproviding the light sources 5015 a and 5015 b in different colors, forexample, blue and red, the difference in heating power can berepresented. The induction-heating cooking device may also be structuredsuch that during the initial stage of heating, one of the systems is litup, and as the heating proceeds, both systems are lit up. Various othermanners of display can be provided by adding blinking patterns.

Next, the relationship between the light conducting body 5014 and thelight source 5015 will be described. The relationship in the sixteenthexample is similar to that in the fifteenth example. The light sources5015 may be provided alternately, with the rest being the same as inFIGS. 32 and 33.

In the fifteenth and sixteenth examples, the light sources are providedin two systems. Three or more systems may be provided. In the case wherethree or more systems are used and are lit up sequentially, the lightmoves as if flowing. This provides a good appearance. However,practically, the number of systems should be about three system or less.When the number of systems is increased, the connection becomescomplicated. When a large number of light sources are used, the cost isundesirably raised.

INDUSTRIAL APPLICABILITY

As is clear from the above-described examples, the present inventionprovides a lit-up display on the cooking board representing a heatingstate. Accordingly, the display which is visually separated from thecooking section in a conventional apparatus can be provided in thevicinity of the cooking section. Thus, the induction-heating cookingdevice can be used in a similar manner to that of a gas cooking device.

According to the present invention, the light conducting means and thelight emitting means are provided below the heating coil. Owing to sucha structure, discoloring, deformation or the like of the lightconducting means caused by radiation, conductance or transmission fromthe cooking container or the like can be prevented. The light emittingmeans formed of a light bulb, a semiconductor device or the like canprevent, for example, malfunction caused by the influence of the strongmagnetic field or reduction in reliability due to self-heat generation.Reduction in the luminous intensity or the like due to a temperaturerise of a semiconductor device or the like used for the light emittingmeans can be prevented. The light beam from the light emitting means canbe prevented from leaking to an area immediately above the lightemitting means.

According to the present invention, the light conducting means isdisc-shaped and has an opening at the center thereof. The light emittingmeans is provided in the opening of the light conducting means. Owing tosuch a structure, a display which is uniform in luminous intensity canbe provided. The display is provided in a shape similar to the shape ofthe heating area, which is usually circular, and the cooking container,which is usually cylindrical. Thus, the effect of visual recognizabilityis further improved.

According to the present invention, the thickness of the lightconducting means is greatest in an inner portion and decreases toward anouter portion. Reflection means is provided on a top surface or a bottomsurface of the light conducting means. Owing to such a structure, theloss of the light beam at the time of incidence is reduced. Thereflective plate reduces the loss of the light beam during propagation.Therefore, a display having a higher luminous intensity with less losscan be efficiently provided.

According to the present invention, the light conducting means has anillumination surface at an outer peripheral end thereof. Owing to such astructure, the propagated light is subjected to total reflection so asto guide the light beam toward the cooking board, i.e., a cookingsurface. Thus, the visual recognizability can be further improved.

According to the present invention, reflection means is providedparallel to the illumination surface provided at the outer peripheralend of the light conducting means. Thus, the loss of the light beamcaused at the time of total reflection due to dispersion duringproduction can be reduced.

According to the present invention, a wall is provided on a top surfaceof the light conducting means so as to guide the light beam toward thecooking board. The light beam is randomly reflected or diffused by thetop surface of the wall. Owing to such a structure, the display can beprovided at a position closer to the cooking board, which improves thevisual recognizability. The random reflection allows the display to bevisually recognizable from various angles.

According to the present invention, a concave surface facing the lightemitting means is provided at a border section of the light conductingmeans, on which the light from the light emitting means is incident.Owing to such a structure, the refraction angle can be larger than theangle of incidence. Thus, even when light emitting means having a smalldirectivity angle is used, a highly luminous, wide range display can beprovided. Furthermore, the number of the light emitting means can bereduced, and thus a low cost device can be provided. Since the lightbeam emitted by the light emitting means is propagated from an innerportion to an outer portion of the light conducting means, a displaywhich is uniform in luminous intensity can be provided.

According to the present invention, the light conducting means is fixedto a coil base. Owing to such a structure, the position of the displayprovided by the light conducting means with respect to the position ofthe heating area can be restricted. This prevents reduction in thethermal efficiency and non-uniformity of the thermal distribution. Sincethe light beam emitted by the light emitting means is propagated from aninner portion to an outer portion of the light conducting means, adisplay which is uniform in luminous intensity can be provided.

According to the present invention, the light conducting means also actsas the coil base. Owing to such a structure, the position of the displayprovided by the light conducting means with respect to the position ofthe heating area can be restricted. Since the light beam emitted by thelight emitting means is propagated from an inner portion to an outerportion of the light conducting means, a display which is uniform inluminous intensity can be provided.

According to the present invention, the light emitting means is fixed tothe light conducting means. Owing to such a structure, the position ofthe light conducting means on which light is incident can be restricted.Thus, the loss of the light beam at the time of incidence can beminimized. Since the light emitting means is provided so as to emitlight in the same direction as the light propagation direction, the lossof the light beam can be further reduced. Since the light beam emittedby the light emitting means is propagated from the center to an outerportion of the light conducting means, a display which is uniform inluminous intensity can be provided.

According to the present invention, reduction in the luminous intensityof the semiconductor device used for the light emitting means, anddiscoloring, deformation and the like of the resin used for the lightconducting means can be prevented from occurring due to thermalinfluences caused by radiation, conductance or transmission from thecooking container or thermal influences caused by self-heat generationof the heating coil. Since the light beam emitted by the light emittingmeans is propagated from the center to an outer portion of the lightconducting means, a display which is uniform in luminous intensity canbe provided.

According to the present invention, a plurality of blocks of the lightconducting means are combined so as to obtain a space. Thus, the coolingperformance can be improved. Blocks each including the light conductingmeans and the light emitting means are used. Therefore, repairing can beeasily and rapidly performed by replacing the block which malfunctions.The repairing cost or the like can be low, and thus the user can obtainbetter service. Since the light beam emitted by the light emitting meansis propagated from the center to an outer portion of the lightconducting means, a display which is uniform in luminous intensity canbe provided.

According to the present invention, when the power is turned on, agraphic pattern is displayed on the cooking board in the vicinity of theheating section. Thus, it is easy to visually recognize that the poweris on. The graphic pattern which is displayed when the power is onchanges its form when heating starts. Therefore, the state where thepower is on can be easily distinguished from the state where the heatingis being performed.

According to the present invention, different rated outputs of theheating coils can be displayed by different graphic patterns provided onthe cooking board by the light emitting means. Thus, visual recognitionof the difference in the rated outputs can be easily done. Since anappropriate heating section is selected in accordance with the type oramount of cooking, appropriate cooking can be performed.

According to the present invention, a light source is combined with alight conducting body for receiving the light from the light source andlighting up a part or the entirety of the outer periphery of the heatingcoil. Owing to such a structure, a clear continuous graphic pattern canbe displayed on the cooking board. Therefore, visual recognition of theheating state can be easily performed. Since the number of the lightsources is minimized, the productivity and cost can be improved.

According to the present invention, a plurality of light sources can bedivided into two systems, and the systems are arranged parallel to eachother. Even when one system malfunctions, the other system allows theheating state to be visually recognized. Such a two-system structurealso increases the freedom in combining different forms of display,using blinking or the like.

1. An induction-heating cooking device, comprising: a light-transmissivecooking board on which a cooking container to be heated is to be placed;a heating coil for heating the cooking container; light emission meansfor emitting a light beam; and light-transmissive light conducting meansfor allowing the light beam emitted by the light emission means to bepropagated therethrough, wherein: the light conducting means isplate-like and guides the light beam from the light emission meanstoward an outer peripheral portion of the light conducting means, thelight beam lights up an outer peripheral portion of the light conductingmeans, the light conducting means includes a wall extending verticallytoward the cooking board from an outer peripheral end thereof, and thelight beam is directed from the top surface of the wall toward thecooking board.
 2. An induction-heating cooking device according to claim1, wherein the light emission means and the cooking board are providedoppositely to each other with respect to the heating coil.
 3. Aninduction-heating cooking device, comprising: a light-transmissivecooking board provided on a top surface of a main body case; a heatingsection provided on the cooking board for heating a cooking containerplaced thereon by induction heating; a heating coil provided oppositelyto the cooking container with respect to the cooking board, the heatingcoil being provided in correspondence with the heating section; aplurality of first light sources and a plurality of second light sourcesfor emitting light beams; and a light conducting body for guiding thelight beams emitted by the plurality of first light sources and theplurality of second light sources and outputting the light beam in anannular form at a position corresponding to an outer peripheral portionof the heating coil, wherein the plurality of first light sources andthe plurality of second light sources are connected parallel to eachother.
 4. An induction-heating cooking device according to claim 3,wherein the plurality of first light sources and the plurality of secondlight sources are connected in the form of blocks.
 5. Aninduction-heating cooking device according to claim 3, wherein: thelight conducting body includes a plurality of light conductive bodypieces, and a plurality of blocks, each including the light conductingbody piece and at least two light sources, are combined.
 6. Aninduction-heating cooking device according to claim 3, wherein: thelight conducting body includes a wall extending vertically toward thecooking board from an outer peripheral end thereof, and the light beamsare directed from the top surface of the wall toward the cooking board.7. An induction-heating cooking device according to claim 3, furthercomprising a plurality of third light sources for emitting light beams,wherein the plurality of first light sources, the plurality of secondlight sources, and the plurality of third light sources sequentiallyblink.
 8. An induction-heating cooking device according to claim 3,further comprising lead sections for connecting the plurality of firstlight sources, wherein the lead sections are provided radially around acenter of the light conducting body.
 9. An induction-heating cookingdevice according to claim 8, wherein each of the lead sections istwisted.
 10. An induction-heating cooking device according to claim 1,wherein the light emission means and the light conducting means areprovided below the heating coil.